Rare-Earth-Encapsulated SIV–TeIV–Templated Polyoxotungstate for Photoelectrochemical Enzyme Biosensor for Glucose Detection

By utilizing a [S^IVO₃]^2- and [Te^IVO₃]^2- mixed-heteroanion strategy, a rare-earth encapsulated S^IV-Te^IV-templated polyoxotungstate [N(CH₃)₄]₁₄K_2.5Na_7.5{[Er₂W₄(H₂O)₇O₉][SW₉O₃₃][TeW₉O₃₃][S_0.5Te_0.5W₉O₃₃]}{[Er₂W₄(H₂O)₇O₉][S_0.5Te_0.5W₉O₃₃]₂[TeW₉O₃₃]}·98 H₂O (1) was synthesized, whose polyoxoanion skeleton is composed of two discrete trimeric Er^III-encapsulated S^IV-Te^IV-templated polyoxotungstate {[Er₂W₄(H₂O)₇O₉][SW₉O₃₃][TeW₉O₃₃][S_0.5Te_0.5W₉O₃₃]}^12- and {[Er₂W₄(H₂O)₇O₉][S_0.5Te_0.5W₉O₃₃]₂[TeW₉O₃₃]}^12- units. It is worth noting that 1 represents the first polyoxotungstate simultaneously incorporating S^IV and Te^IV heteroatoms in the polyoxometalate family. Moreover, its application in photoelectrochemical (PEC) biosensor was explored by sonicating 1 into nanosized crystals (nano-1). Subsequently, a Au/nano-1/PbS composite material comprising nano-1, lead sulfide (PbS) and Au nanoparticles (AuNPs) was prepared, which was utilized to construct a PEC sensor for detecting hydrogen peroxide with a detection limit of 2.331 μM and the detection range from 5 × 10^-6 to 5 × 10^-4 M. Soon afterward, by immobilizing glucose oxidase, an enzyme-based PEC sensor was developed for glucose detection, demonstrating outstanding performance with a low detection limit of 3.142 nM. This work not only provides a new strategy for synthesizing complicated polyoxometalates containing different heteroatoms, but also highlights the potential of polyoxometalate-based materials for PEC biosensor applications.